Extended treatment zone catheter

ABSTRACT

A catheter having an extended treatment zone for cooling tissue is provided. The catheter includes an elongate catheter body having a distal tip, and a fluid injection conduit disposed inside the catheter body defining a return lumen therein. The fluid injection conduit further defines two or more injection orifices including a first distal orifice near the distal tip, and a second orifice longitudinally offset along the fluid injection conduit to be less proximate the distal tip than the first orifice. Fluid cryogen flowing through the orifices creates an extended tissue cooling contour about the distal end portion of the catheter. At least one ECG ring electrode is provided about the catheter body near the second orifice. The catheter may thus provide for electrocardiographic mapping of tissue nodes lying transversely between the distal tip and the ECG ring electrode.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. patent applicationSer. No. 10/338,274, filed Jan. 8, 2003 now U.S. Pat. No. 6,899,709,entitled COOLANT INJECTION, which is a continuation of U.S. patentapplication Ser. No. 09/850,668, filed May 7, 2001, now issued U.S. Pat.No. 6,540,740, entitled CRYOSURGICAL CATHETER, which is a continuationof U.S. patent application Ser. No. 09/201,071, filed Nov. 30, 1998, nowissued U.S. Pat. No. 6,235,019, entitled CRYOSURGICAL CATHETER, which isa continuation of U.S. patent application Ser. No. 08/893,825, filedJul. 11, 1997, now issued U.S. Pat. No. 5,899,899, entitled CRYOSURGICALLINEAR ABLATION STRUCTURE, which is a continuation-in-part of U.S.patent application Ser. No. 08/807,382, filed Feb. 27, 1997, now issuedU.S. Pat. No. 5,899,898, and entitled CRYOSURGICAL LINEAR ABLATION, allof which are incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

n/a

FIELD OF THE INVENTION

The invention relates to catheters, and more particularly tocryosurgical catheters used for tissue ablation.

BACKGROUND OF THE INVENTION

Many medical procedures are performed using minimally invasive surgicaltechniques, wherein one or more slender implements are inserted throughone or more small incisions into a patient's body. With respect toablation, the surgical implement can include a rigid or flexiblestructure having an ablation device at or near its distal end that isplaced adjacent to the tissue to be ablated. Radio frequency energy,microwave energy, laser energy, extreme heat, and extreme cold can beprovided by the ablation device to kill the tissue.

With respect to cardiac procedures, a cardiac arrhythmia can be treatedthrough selective ablation of cardiac tissue to eliminate the source ofthe arrhythmia. A popular minimally invasive procedure, radio frequency(RF) catheter ablation, includes a preliminary step of conventionalelectrocardiographic mapping followed by the creation of one or moreablated regions (lesions) in the cardiac tissue using RF energy.Multiple lesions are frequently required because the effectiveness ofeach of the proposed lesion sites cannot be predetermined due tolimitations of conventional electrocardiographic mapping. Often, fivelesions, and sometimes as many as twenty lesions may be required beforea successful result is attained. Usually only one of the lesions isactually effective; the other lesions result in unnecessarily destroyedcardiac tissue.

Deficiencies of radio frequency ablation devices and techniques havebeen overcome by using cold to do zero degree or ice mapping prior tocreating lesions, as taught in U.S. Pat. Nos. 5,423,807; and 5,281,213;and 5,281,215. However, even though combined cryogenic mapping andablation devices permit greater certainty and less tissue damage than RFdevices and techniques, both the cryogenic and the RF devices areconfigured for spot or roughly circular tissue ablation.

Spot tissue ablation is acceptable for certain procedures. However,other procedures can be more therapeutically effective if multiple spotlesions along a predetermined line, or a single elongate or linearlesion is created in a single ablative step. Radio frequency ablationdevices are known to be able to create linear lesions by dragging theablation tip along a line while it is active. However, no cryogenicdevices are known that are optimized for, or which are even minimallycapable of, creating an elongate lesion.

Furthermore, when using a catheter to simultaneously performelectrocardiographic mapping as well as to treat tissue being mapped,the treatment zone extending around the catheter is limited. This isespecially problematic with regard to bipolar or multipolar electrodecatheters having multiple electrocardiogram (ECG) leads disposed at thedistal tip. The arrangement of the ECG leads around the distal tip inrelation to the tissue treatment element is such that once a tissue nodeof interest has been mapped, the catheter's treatment zone extendingaround the distal tip is generally not large enough or shaped toencompass the tissue node. The catheter must be moved of repositioned toeffectuate treatment. It would be desirable therefore, to provide acatheter having the electrocardiographic mapping capabilities asdiscussed above in addition to an extended treatment zone to as tobetter perform the twin functions of mapping and treatment or ablationof tissue.

SUMMARY OF THE INVENTION

The present invention provides a cryogenic catheter having an elongateouter member and a plurality of inner members disposed within theelongate outer member. The inner members have a plurality ofcontrollable openings formed thereon for the selective release ofcryogenic fluid. A plurality of electrode members is disposed on anexternal surface of the outer member. The inner members may bepositioned in a staggered configuration or alternatively at least oneinner member may be disposed within another inner member. In such aconfiguration, one of the inner members may be slidable or rotatable tothe other.

DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention, and theattendant advantages and features thereof, will be more readilyunderstood by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings wherein:

FIG. 1 is a schematic illustration of an embodiment of a cryosurgicalsystem in accordance with the invention;

FIG. 2 is a schematic depiction of the chambers of the heart showingplacement of the catheter of FIG. 1;

FIG. 3 illustrates the tip region of one embodiment of the catheter inaccordance with the invention;

FIG. 4 illustrates an alternative embodiment of the catheter of FIG. 3;

FIG. 5 illustrates yet another embodiment of the catheter;

FIG. 6 illustrates a deformable tip for a catheter;

FIG. 7 illustrates yet another embodiment of the catheter;

FIG. 8 is a sectional view of the catheter of FIG. 7 taken along line8-8;

FIG. 9 is a sectional view of an alternative embodiment of the linearablation catheter illustrated in FIG. 7;

FIG. 10 illustrates an expansion chamber within a portion of a helicalcoil;

FIG. 11 illustrates a portion of a catheter having an elongate,thermally-transmissive strip;

FIG. 12 is a sectional view of the catheter of FIG. 3 taken along line12-12;

FIG. 13 is a sectional view of the catheter of FIG. 3 taken along line13-13;

FIGS. 14-16 are sectional views of additional catheter embodiments;

FIG. 17 illustrates an inner face of a flexible catheter member;

FIG. 18 depicts yet another embodiment of a catheter in accordance withthe invention;

FIG. 19 is a table illustrating cooling performance of a catheter inaccordance with the invention;

FIG. 20 is a sectional view of another catheter embodiment;

FIG. 21 is a sectional view of a portion of the catheter of FIG. 20;

FIG. 22 is a detailed view of an area of the catheter portionillustrated in FIG. 21;

FIG. 23 is an illustration of yet another catheter embodiment;

FIG. 24 depicts still another catheter embodiment;

FIG. 25 illustrates yet another embodiment of the catheter;

FIG. 26 is a sectional view of the catheter of FIG. 25 taken along line26-26;

FIG. 27 illustrates yet still another embodiment of the catheter;

FIG. 28 illustrates the catheter of FIG. 27 in a second configuration;

FIG. 29 is a sectional view of the catheter of FIG. 28 taken along line29-29;

FIG. 30 is a sectional view of the catheter of FIG. 28 taken along line30-30;

FIG. 31 illustrates yet another embodiment of the catheter;

FIG. 32 illustrates the catheter of FIG. 31 in a second configuration;

FIG. 33 is a sectional view of the catheter of FIG. 32 taken along line33-33;

FIG. 34 is a sectional view of the catheter of FIG. 32 taken along line34-34;

FIG. 35 illustrates yet another embodiment of the catheter;

FIG. 36 is a sectional view of yet another embodiment of the catheter;

FIG. 37 is a sectional view of the catheter of FIG. 36 after rotation;

FIG. 38 illustrates yet another embodiment of the catheter;

FIG. 39 illustrates the catheter of FIG. 38 in a second configuration;

FIG. 40 illustrates one embodiment of the catheter proximate a treatmentnode, with a limited treatment zone shown around the catheter;

FIG. 41 illustrates another embodiment of the catheter proximate thetreatment node of FIG. 40, with an extended treatment zone provided bythe catheter;

FIG. 42 illustrates an expanded cross-sectional view of the catheter ofFIG. 41, taken along lines A-A in FIG. 41;

FIGS. 43A and 43B are perspective views of two addition embodiments ofthe flow conduit of the catheter of FIG. 42; and

FIG. 44 illustrates a cross-sectional view of yet another embodiment ofthe catheter

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic illustration of a cryosurgical system inaccordance with the invention. The system includes a supply of cryogenicor cooling fluid 10 in communication with the proximal end 12 of aflexible catheter 14. A fluid controller 16 is interposed or in-linebetween the cryogenic fluid supply 10 and the catheter 14 for regulatingthe flow of cryogenic fluid into the catheter in response to acontroller command. Controller commands can include programmedinstructions, sensor signals, and manual user input. For example, thefluid controller 16 can be programmed or configured to increase anddecrease the pressure of the fluid by predetermined pressure incrementsover predetermined time intervals. In another exemplary embodiment, thefluid controller 16 can be responsive to input from a foot pedal 18 topermit flow of the cryogenic fluid into the catheter 14. One or moretemperature sensors 20 in electrical communication with the controller16 can be provided to regulate or terminate the flow of cryogenic fluidinto the catheter 14 when a predetermined temperature at a selectedpoint or points on or within the catheter is/are obtained. For example atemperature sensor can be placed at a point proximate the distal end 22of the catheter and other temperature sensors 20 can be placed at spacedintervals between the distal end of the catheter and another point thatis between the distal end and the proximal end.

The cryogenic fluid can be in a liquid or a gas state. An extremely lowtemperature can be achieved within the catheter, and more particularlyon the surface of the catheter by cooling the fluid to a predeterminedtemperature prior to its introduction into the catheter, by allowing aliquid state cryogenic fluid to boil or vaporize, or by allowing a gasstate cryogenic fluid to expand. Exemplary liquids includechlorodifluoromethane, polydimethylsiloxane, ethyl alcohol, HFC's suchas AZ-20 (a 50-50 mixture of difluoromethane & pentafluoroethane sold byAllied Signal), and CFC's such as DuPont's FREON. Exemplary gassesinclude nitrous oxide, and carbon dioxide.

The catheter 14 includes a flexible member 24 having athermally-transmissive region 26 and a fluid path through the flexiblemember to the thermally-transmissive region. A fluid path is alsoprovided from the thermally-transmissive region to a point external tothe catheter, such as the proximal end 12. Although described in greaterdetail below, exemplary fluid paths can be one or more channels definedby the flexible member 24, and/or by one or more additional flexiblemembers that are internal to the first flexible member 24. Also, eventhough many materials and structures can be thermally conductive orthermally transmissive if chilled to a very low temperature and/or coldsoaked, as used herein, a “thermally-transmissive region” is intended tobroadly encompass any structure or region of the catheter 14 thatreadily conducts heat.

For example, a metal structure exposed (directly or indirectly) to thecryogenic fluid path is considered a thermally-transmissive region 26even if an adjacent polymeric or latex catheter portion also permitsheat transfer, but to a much lesser extent than the metal. Thus, thethermally-transmissive region 26 can be viewed as a relative term tocompare the heat transfer characteristics of different catheter regionsor structures.

Furthermore, while the thermally-transmissive region 26 can include asingle, continuous, and uninterrupted surface or structure, it can alsoinclude multiple, discrete, thermally-transmissive structures thatcollectively define a thermally-transmissive region that is elongate orlinear. Depending on the ability of the cryogenic system, or portionsthereof, to handle given thermal loads, the ablation of an elongatetissue path can be performed in a single or multiple cycle processwithout having to relocate the catheter one or more times or drag itacross tissue. Additional details of the thermally-transmissive region26 and the thermal transfer process are described in greater detailbelow.

In exemplary embodiments of the invention, the thermally-transmissiveregion 26 of the catheter 14 is deformable. An exemplary deformation isfrom a linear configuration to an arcuate configuration and isaccomplished using mechanical and/or electrical devices known to thoseskilled in the art. For example, a wall portion of the flexible member24 can include a metal braid to make the catheter torqueable for overallcatheter steering and placement. Additionally, a cord, wire or cable canbe incorporated with, or inserted into, the catheter for deformation ofthe thermally transmissive region 26.

The cryogenic system of FIG. 1 is better understood with reference toits use in an operative procedure as shown in FIG. 2. Following thedetermination of a proposed lesion site within a heart chamber 28, forexample, the catheter 14 is directed through a blood vessel 30 to aregion within the heart, such as an atrial or ventricular chamber, wherethe lesion will be made. The thermally-transmissive region 26 is placedproximate to the tissue to be ablated. The thermally-transmissive regionof the catheter may be deformed to conform to the curvature of thetissue before, during, or after placement against the tissue. Thecontroller 16 allows or causes cryogenic fluid to flow from thecryogenic fluid supply 10 to the fluid path in the catheter 14 andthence to the thermally-transmissive region 26 to ablate the desiredarea or to cold map along the same tissue area. In one embodiment (e.g.,FIG. 12) a first conduit is concentric within a second conduit andcooling fluid travels to a thermally-transmissive region proximate aclosed distal end of the catheter through a first conduit (fluid path)and is exhausted from the catheter through the second conduit (fluidpath).

Having described the function of the cryogenic catheter 14 and its usein a system context, several exemplary embodiments of thethermally-transmissive region 26 of the catheter are now described ingreater detail. FIGS. 3, 4, 5, 12-16 and 18 illustrate embodiments ofthe catheter, or portions thereof, having two or morethermally-transmissive segments in a spaced-apart relationship. Each ofthe illustrated catheters includes a closed tip 32 that can include athermally-transmissive material.

Referring specifically to the embodiment depicted in FIG. 3, multiplethermally-transmissive elements 34 are integral with a distal portion ofa catheter. Each of the thermally-transmissive elements 34 includes afirst side or face 36 (shown in FIGS. 12 and 13) exposed to a cryogenicfluid path and cryogenic fluid (shown by arrows) and a second side orface 38 exposed to points exterior to the catheter. As shown in FIG. 13,the first side 36 and/or second side 38 of any or all of thethermally-transmissive elements 34 can be substantially flush with,recessed below, or protruding from the inner surface 40 and outersurface 42 of a portion of the catheter. The thermally-transmissiveelements 34 are separated by flexible portions of material 44 than canrange from slightly less thermally-transmissive than the adjacentthermally-transmissive elements to substantially lessthermally-transmissive than the adjacent elements. In the illustratedembodiment of FIG. 3, the thermally-transmissive elements 34 areannular, cylindrical elements which are made of gold-plated copper,bronze, or stainless steel. Thermocouples 35 can be associated with oneor more of the elements 34 and the tip 32. The thermally-transmissiveelements 34 can be completely exposed, embedded, or a combinationthereof along the full 360 .degree. of the catheter's circumference. Incertain applications the thermally-transmissive elements traverse ordefine less than 360 .degree. of the catheter's circumference as shownin FIGS. 14-16 and as described below. The longitudinal width of eachthermally-transmissive element 34, the spacing between elements, thematerial thickness, and the material composition are matched with aselected cryogenic fluid, one or more cryogenic fluid delivery locationswithin the catheter and fluid delivery pressure to produce overlappingcold regions which produce a linear lesion.

The embodiment illustrated in FIG. 4 is substantially identical to theembodiment of FIG. 3, however, at least one of thethermally-transmissive elements 34 includes a first open end 46 thatdefines a first plane and a second open end 48 that defines a secondplane, wherein the first and second planes intersect to give the annularelements a wedge-like appearance. Such a configuration permits adjacentthermally-transmissive elements 34 to be positioned very closelytogether, but it can limit the possibilities for deforming thethermally-transmissive region 26, which, in this embodiment, is flexiblein the direction indicated by the arrow.

With respect to the embodiments shown in both FIGS. 3 and 4, thethermally-transmissive elements 34 are substantially rigid and areseparated and/or joined by a flexible material 44. However, in otherembodiments the thermally-transmissive elements 34 are flexible and areinterdigitated with either rigid or flexible segments. FIG. 5, forexample, illustrates an embodiment of the cryogenic catheter havingthree thermally-transmissive elements 34 that are flexible. Theflexibility is provided by a folded or bellows-like structure 50. Inaddition to being shapable, a metal bellows can have enough stiffness toretain a selected shape after a deforming or bending step.

Instead of, or in addition to, flexible, thermally-transmissive elements34 and/or flexible material 44 between elements, the distal tip 32 (or aportion thereof) can be deformable. For example, FIG. 6 illustrates atip 32 having thermally-transmissive, flexible, bellows 50.

Referring now to FIGS. 7-10, a different approach is shown for providingmultiple thermally-transmissive segments in a spaced-apart relationship.FIG. 7 illustrates a catheter embodiment having an elongate,thermally-transmissive region 26 that includes a helical coil 52 atleast partially embedded in the flexible member 24. As shown in FIG. 8,at least a first portion 54 of the helical coil 52 is exposed to a fluidpath within the flexible member 24 and a second portion 56 of thehelical coil is exposed to the exterior of the flexible member. Asdescribed above with respect to FIG. 13, the first portion 54 of thecoil can be substantially flush with, recessed below, or protruding froman inner surface 58 of the flexible member 24. Similarly, the secondportion 56 of the coil 52 can be substantially flush with, recessedbelow, or protruding from an outer surface 60 of the flexible member 24.

In the embodiment of FIG. 8, the second portion 56 of the coil 52 isexposed along only a portion of the outer circumference of the flexiblemember 24 to define a longitudinally-elongate, thermally-transmissiveregion 26. This configuration can be provided by eccentrically matingthe helical coil 52 to the catheter so that the longitudinal axis of thecoil and the longitudinal axis of the catheter are substantiallyparallel. The eccentric positioning of the coil 52 provides excellentcooling performance because the surface area available for thermalexchange between the first portion 54 of coil and the cryogenic fluid isgreater than the surface area available for thermal exchange between thesecond portion 56 of the coil and adjacent tissue where cooling power isdelivered by each exposed coil portion to provide a linear lesion.

Referring now to FIG. 9, an alternative embodiment is shown wherein afirst portion 62 of the coil 52 is exposed around the entirecircumference of the flexible member 24, and a second portion 64 isexposed to a fluid path around the inner surface of the flexible member24. This is achieved by having the longitudinal axis of the helical coil52 co-axial with the longitudinal axis of the catheter.

In the embodiments illustrated in FIGS. 7-9, the coil 52 is solid.However, in other embodiments the coil can be an elongate, hollow, gasexpansion chamber. For example, FIG. 10 illustrates a portion of ahelical coil 52 that includes a passage that defines at least a portionof a fluid path through a flexible member of the catheter. The coil 52defines a first fluid path diameter at a fluid entry point 66 and asecond fluid path diameter that is greater than the first fluid pathdiameter at a gas expansion or boiling location 68. Gas escaping from afluid exit point 70 can be exhausted through an open central region ofthe coil and/or another passage through the flexible member 24.

FIG. 11 illustrates an embodiment of the catheter wherein a continuous,elongate, thermally-transmissive strip 72 is longitudinally integratedwith a flexible member 24. The strip can include a bellows-likestructure. As described above with respect to other embodiments, a firstportion of the strip can be substantially flush with, recessed below, orprotrude from the outer surface of the flexible member. Similarly, asecond portion of the strip can be substantially flush with, recessedbelow, or protrude from an inner surface of the flexible member.

Referring now to FIG. 12, an embodiment of the catheter is illustratedhaving a second or inner flexible member 74 within a lumen of first orouter flexible member 24, wherein the second flexible member defines afluid path to the thermally-transmissive region 26. The inner member 74can include a single opening 76 at or near the tip 32. Cryogenic fluidis expelled from the opening 76 and returns to the proximal end of thecatheter along a fluid path defined by the outer wall of the innermember 74 and the inner wall of the outer member 24. This fluid pathconfiguration is also partially illustrated in FIGS. 8, 9, and 13.Alternatively, as also shown in FIG. 12, the inner member 74 can beprovided with multiple openings 78 proximate to and/or aligned with theinner face of one or more thermally-transmissive elements 34 to achievemore uniform cooling across the entire elongate, thermally-transmissiveregion 26.

Referring now to FIGS. 14-16, sectional views of catheter embodimentsare illustrated to show alternative configurations forthermally-transmissive elements. The previously describedthermally-transmissive elements 34 are arcuate and form complete andcontinuous 360 degree structures that traverse the completecircumference of the catheter, notwithstanding being flush with,depressed below, or raised above the outermost surface of the flexiblemember 24. However, the arcuate elements 34′, 34″, and 34′″ illustratedin FIGS. 14-16, respectively, traverse less than 360 degrees of thecircumference of the first flexible member and do not form completeloops. For example, in FIG. 14, element 34′ defines an approximately 270degree arc. In FIG. 15 the thermally-transmissive element 34″ defines anapproximately 180 degree arc; and in FIG. 16, the thermally-transmissiveelement 34″′ defines an approximately 90 degree arc. A catheter caninclude combinations of element types, such as a complete ring or loopelement, a 270 degree element and a 180 degree element as desired todefine a thermally transmissive region. In addition to the havingapplicability with respect to rigid thermally-transmissive elements, thebellows-like elements can also be less than 360 degrees.

The less than 360 degree arcuate elements provide unique functionalbenefits with respect to thermal transfer and flexibility of thethermally-transmissive region. For example, because the portion of thecatheter between the opposing ends of element 34′, 34″, 34′″ does notinclude a rigid structure, but rather only the resilient material offlexible member 24, the thermally-transmissive region of the cathetercan be more tightly curved (gap between ends inward and element facingoutward) than it could with complete 360 degree structures, especiallyif the elements are relatively long longitudinally.

The inner member 74 can be adapted to direct cooling fluid at only thethermally transmissive element(s) and the shape and/or the number ofopenings for cooling fluid can be configured differently depending onthe length of the arc defined by the thermally-transmissive element(s).For example, FIG. 14 illustrates an embodiment of the inner memberhaving three openings opposing the thermally transmissive element 34′;FIG. 15 illustrates two openings for a smaller arc; and FIG. 16discloses a single opening for an even smaller arc.

Another advantage to providing one or more thermally-transmissiveelements that have a less than 360 degree configuration is that limitingthe span of the elements to a desired lesion width, or somewhat greaterthan a desired lesion width, reduces the thermal load on the systemand/or permits colder temperatures to be achieved than with respect to acomplete 360 degree structure. Unnecessary and perhaps undesirablecooling does not occur at any other location along the catheter exceptat an elongate region of predetermined width. A similar effect can alsobe achieved by providing a non-circular 360 degree element or byeccentrically mounting a circular 360 degree element with respect to theflexible member, wherein a portion of the 360 degree element is embeddedwithin the wall of the flexible member or otherwise insulated from thecryogenic fluid path in a manner similar to that shown in FIG. 8.

Referring now to FIG. 17, a portion of the inner face of an outerflexible member showing in an exemplary embodiment, thermal transferpins 80 protruding from the inner face of a thermally-transmissiveelement 34. The pins permit thermal transfer through the flexible member24. As with the other features of the invention, the pins are equallysuitable for complete 360 degree element structures or less than 360degree structures. Although only pins are shown on any geometric orsurface means to increase heat transfer including but not limited topins, irregularities, channels or surface modifications may be used.Referring now to FIG. 18, yet another embodiment of the catheter isshown wherein rigid metal rings 34 a-c are interdigitated with flexiblesegments 44 a-c to define a first flexible member and athermally-transmissive region approximately one inch in length. A secondflexible member is concentric within the first flexible member and hasan outlet for cryogenic fluid at its distal end. Thermocouples 82 a-ccan be associated with one or more of the rings 34 a-c.

It has been described above how the thermal loading of a cooling systemcan be reduced by providing thermally-transmissive elements that spanless than 360 degrees. However, the thermal loading can also be reducedby sequentially cooling the thermally-transmissive region. One way tosequentially cool is to modulate the pressure of the cooling fluid alongthe fluid path through the flexible member. This modulation can beperformed by the fluid controller which can be programmed to increaseand decrease the pressure of the fluid by predetermined pressureincrements over predetermined time intervals. When the cryogenic fluidis a liquid that provides cooling by changing phase from liquid to gas,the change of pressure alters the physical location along the fluid pathwhere the phase change takes place and concomitantly changes the pointof coldest temperature along the thermally-transmissive region. Thus,varying the pressure of the fluid can provide a moving ice-formation“front” along the catheter, enabling the creation of a linear lesion.

Therefore, a method of forming an elongate tissue lesion can include thefollowing steps using any of the above described catheters having anelongate, thermally-transmissive region. In a first step a cryogenicfluid is introduced into the flexible member at a first predeterminedpressure. Next, the pressure of the cryogenic fluid is incrementallyincreased within the flexible member until a second predeterminedpressure is achieved. Similarly, the pressure of the cryogenic fluidwithin the flexible member can be decreased incrementally from thesecond predetermined pressure to the first predetermined pressure,wherein the steps of incrementally increasing and decreasing thepressure define a thermal cycle. Typically, from one to eight thermalcycles are required to achieve a desired therapeutic effect. In anexemplary method, about ten increments of about five seconds in durationare selected and pressure is increased by about 20 to 40 pounds persquare inch in each increment. Thus, using this method an elongatelesion can be created in less than 20 minutes.

FIG. 19 is a table that illustrates sequential cooling in a catheter asdescribed above having a thermally-transmissive region that includes atip and three elements or rings. The table illustrates three testsconducted in a still bath at 37 .degree. C., using AZ-20 as thecryogenic fluid. Alternatively, nitrous oxide could be used as thecryogenic fluid. Associated with each pressure increment are measuredtemperatures at the tip, first ring, second ring, and third ring. Theshaded region illustrates the sequential movement of a targettemperature range (upper −40's to low −50's or lower) in response to achange in pressure. Although values are only provided for three rings, asimilar effect and pattern is obtained with more than three rings orelements.

Turning now to FIG. 20, a thermally-transmissive portion of anotherembodiment of a medical device or structure such as a catheter isillustrated in a sectional view. The structure can include an innerpassage or lumen as described above with respect to other embodiments,but which is not shown in this illustration for purposes of clarity.Thus, the illustrated portion is the outer passage or lumen that definesan elongate ablation region. Thermally-transmissive elements 84, such asgold plated copper, are joined to adjacent elements by resilientconnecting elements 86, such as a stainless steel springs welded to theends of the elements 84. A resilient bio-compatible material 88 coversthe connecting elements 86 and the interstices between adjacentthermally-transmissive elements. In an exemplary embodiment, thematerial 88 is vulcanized silicone. It should be noted in theillustration that the surface of the elements 84 is contiguous andco-planar with the material 88 to provide a smooth outer surface.

FIG. 21 illustrates a single thermally-transmissive element 84 havingreduced diameter ends 90 and 92. The wider central portion 94 providesan expansion chamber for gas (shown by arrows) exiting an aperturedinner passage 96. FIG. 22 shows additional detail of the end 90 of theelement 84. The end 90 is textured, such as by providing serrations 98,to provide a good adhesion surface for the material 88.

Referring now to FIG. 23, a thermally-transmissive portion of yetanother embodiment of a flexible cryogenic structure is illustrated in asectional view. In this embodiment an inner, apertured structure 100 hasa flat wire 102 wrapped around it in a spiral manner.Thermally-transmissive segments 104 are disposed upon the wire 102 in aspaced-apart relationship, and a flexible, bio-compatible material 106fills the interstices between segments 104. A thermocouple 108 can beassociated with each segment 104. A wire 109 connects the thermocouple108 to instrumentation near the proximal end of the structure. Theexterior surface of the structure is smooth, and the structure caninclude 3 to 12 segments 104. In an exemplary embodiment the innerstructure 100 is made of PTFE, the material 106 is 33 D PEBAX, and thewire 102 is stainless steel or Nitinol. An apertured inner passage(similar to that shown in FIG. 21) is placed within the structure.

FIG. 24 illustrates still another embodiment of a cryogenic coolingstructure that includes a surface or wall 110 including a polymer orelastomer that is thin enough to permit thermal transfer. For example,polyamide, PET, or PTFE having a thickness of a typical angioplastyballoon or less (below 0.006 inches) provides acceptable thermaltransfer. However, the thinness of the wall 110 allows it to readilycollapse or otherwise deform under vacuum or near vacuum conditionsapplied to evacuate fluid/gas from the structure. Accordingly, thestructure is provided with one or more supporting elements 112 such as aspring. The cooling structure is illustrated in association with acatheter 114 having a closed distal tip 116 and mono or bipolar ECGrings 118, 120, 122. The thermally-transmissive region is approximately30 mm in length and is effective for thermal transfer over its entirecircumference. However, as illustrated in FIG. 11, thethermally-transmissive region can be confined to specific region(s) ofthe device's circumference.

Referring now to FIG. 25, an embodiment of the catheter is illustratedhaving three flexible members or injection tubes 210, 211 and 212disposed within a first or outer flexible member 200. In an exemplaryembodiment, the inner flexible members 210, 211 and 212 are arranged ina staggered configuration within the outer flexible member 200. As usedherein, term “staggered” may be used to designate both alinearly/axially staggered configuration or alternatively, arotationally staggered configuration. The flexible members 210, 211 and212 thus define multiple staggered fluid paths within the outer member200. In such a configuration, the injection tubes 210, 211 and 212 allowfor greater aggregate cooling power as well as the creation of a varietyof different cooling/freeze zones 201, 203 and 205 along the length ofthe outer flexible member 200. In an exemplary embodiment, thermocouples204 disposed along the outer surface of the outer flexible member 200may be integrated with an internal feedback loop to provide independentand variable regulation of these freeze zones.

In an exemplary embodiment, the first inner member 210 includes at leastone opening 214 positioned proximate an electrode ring member 207.Cryogenic fluid is expelled from the opening 214 and returns to theproximal end of the catheter along a fluid path defined by the innerwall 218 of the outer member 200, as shown in FIG. 26. Similarly, thesecond inner member 211 includes at least one opening 215 positionedproximate a second electrode ring member 208. Cryogenic fluid is alsoexpelled from the opening 215 and returns to the proximal end of thecatheter along the fluid path defined by the inner wall 218 of the outermember 200. Similarly, the third inner member 212 includes at least oneopening 216 positioned proximate a third electrode ring member 209.

Alternatively, the catheter can be provided with only two inner members,or four or more inner members, not shown, disposed within the outermember. The inner members would have one or more openings proximate toand/or aligned with the inner face of one or more transmissive elements,as described earlier herein, to achieve different regions of freezezones across the entire elongate member. Alternatively, all thestaggered inner members may be simultaneously provided with cryogenicfluid to create a linear lesion for selected applications. The flow ofcooling fluid along the fluid paths through the flexible members canalso be alternated in any number of patterns among the multiple innermembers to provide a desired cooling pattern such as a discontinuous ora continuous lesion across the entire catheter.

In an exemplary embodiment, a catheter with a plurality of thermallyconductive electrode rings would have an underlying injection tube ortubes controlling the release of cryogenic fluid to each electrode. Sucha catheter could be placed in the coronary sinus or endocardially alongthe atrioventricular junction. Once positioned, an electrogram ofinterest is located using a specific electrode ring on the catheter.Coldmapping may be performed on the selected location to confirm thecorrectness of the location. Once, confirmed, the area is cryoablatedusing the same electrode ring. The same embodiments and others describedherein are equally suited to other organs besides the heart and/or anybody portion that would benefit from the application of thermal energy.

Referring now to FIG. 27, an embodiment of the catheter is illustratedhaving an outer member 220 with a fixed injection tube 230 disposedwithin a slidable sheath or overtube 240 therein. The injection tube andovertube are shown spaced apart for illustrative purposes only.Preferably, the injection tube is sized so that an outer surface of theinjection tube engages an inner surface of the overtube while stillallowing one member to slide or rotate relative to the other.

The fixed injection tube 230 has multiple openings 232, 234 formedthereon and the slidable overtube also has multiple openings or ports242, 244 formed thereon. In one configuration shown in FIG. 27, opening232 on the injection tube 230 coincides or is aligned with opening 242on the slidable overtube 240. Thus, any fluid exiting the injection tube230 from opening 232 is able to escape through opening 242.

As the slidable overtube 240 is slid or moved in a first direction asshown by arrow 236 along longitudinal axis 222, opening 232 is coveredor blocked by the surface of overtube 240 as now shown in FIG. 28. In asecond configuration shown in FIG. 29, opening 234 of injection tube 230is aligned with opening 244 of overtube 240. In the same configuration,as shown in FIG. 30, opening 242 is not aligned with any opening formedon the surface of injection tube 230. Although only shown in twopositions or configurations, the slidable overtube is positionable inany number of positions relative to the fixed injection tube. Theovertube may also be used to partially cover the openings on theinjection tube to provide for a limited or controlled flow of cryogenicfluid.

Depending on which opening of the injection tube is aligned with theopenings formed on the overtube, cryogenic fluid is expelled from theopening and returns to the proximal end of the catheter along a fluidpath defined by the inner wall 226 of the outer member 220. Thenon-aligned opening will not expel fluid since the opening will beblocked. Alternatively, the injection tube and overtube can be providedwith three or more openings to achieve multiple cooling/freeze zonesalong the length of the catheter.

Referring now to FIG. 31, an embodiment of the catheter is illustratedhaving a slidable injection tube 260 disposed within a fixed sheath orovertube 270. As shown in FIG. 31, both the injection tube 260 andovertube 270 are disposed within a flexible outer member 250. Theslidable injection tube 260 has multiple openings 262, 264 formedthereon which allows for the release of cryogenic fluid. The fixedovertube 270 also has multiple perforations or openings 272, 274 formedthereon which allows for the differential release of fluid as describedin more detail below. The injection tube may be further provided with athermistor 254 disposed proximate the distal end of the tube to providethermistor feedback. In one embodiment, the openings can be controlledby miniaturized means such as micro or nanovalves.

In a first configuration shown in FIG. 31, opening 262 of the injectiontube 260 coincides or is aligned with opening 274 of the fixed overtube270. As the slidable injection tube 260 is slid or moved in a firstdirection as shown by arrow 266, opening 262 is then aligned withcorresponding opening 272 on the overtube 270 in FIG. 32.

In this second configuration, as shown in FIGS. 32-34, openings 262, 264of injection tube 260 are aligned with openings 272, 274 of overtube270. Although only two configurations for the catheter are shown, theinjection tube 260 is positionable in any number of locations relativeto the fixed overtube 270.

In operation, cryogenic fluid is expelled from the openings and returnsto the proximal end of the catheter along a fluid path defined by aninner wall 256 of the outer member 250. Alternatively, the injectiontube 260 and overtube 270 can be provided with multiple openingsproximate to and/or aligned with the inner face of one or morethermally-transmissive elements as described earlier herein to achievemore uniform cooling across the entire elongate, thermally-transmissiveregion.

Referring to FIG. 35, an embodiment of the catheter is illustratedhaving an outer member 280 with an injection tube 290 with multipleopposed openings 292-297 formed therein. Either the injection tube 290or the overtube 300 may be slidable in a longitudinal plane to exposeand/or cover one or more of the opposed openings on the injection tube290. For example, as shown in FIG. 35, openings 294, 295 formed on theinjection tube 290 are aligned with openings 302, 303 formed on theovertube 230. Furthermore, the injection tube may be positioned in aforwardmost position, not shown, to expose openings on the injectiontube proximate the tip of the catheter. In this configuration, theinjection tube would provide fluid to cool the area around the tip ofthe catheter.

In the embodiments described and shown above in FIGS. 32-35, electroderings as shown in FIG. 25 may be provided along the outer surface of anyof the outer members. The electrodes would serve both as electricalconductors and as a thermal transmitter at each location.

Referring to FIGS. 36 and 37, an embodiment of the catheter isillustrated have one or more rotatable members disposed within aflexible outer member 310. In this embodiment, the catheter includes anovertube member 312 and an injection tube member 314, one or both ofwhich are rotatable with respect to one another. In an exemplaryembodiment as shown in FIGS. 36 and 37, the injection tube 314 isrotatable relative to the fixed overtube 312. The injection tube 314 maybe rotatable in either or both a clockwise and counterclockwisedirection as indicated by arrows 320 and 322. As shown in FIG. 36, in afirst configuration, opening 316 formed on the overtube 312 aligns withan opening 318 formed on the injection tube 314. As the injection tube314 is rotated in a counterclockwise direction, the opening 318 on theinjection tube 314 is placed out of alignment with the opening 316formed on overtube 312, as shown in FIG. 37. Alternatively, theinjection tube 314 may be fixed in the catheter while the overtube 312is rotatable. In another embodiment, both the injection tube andovertube may both be rotatable. In yet a further embodiment, theinjection tube and/or the overtube are rotatable and slidable within theouter member.

In the embodiments shown and described above, the slidable and rotatableinner and outer tubes may have openings so arranged as to allow thefluid releasing openings to be in a variety of open and closedconfigurations with a minimum of relational movement between the tubes.For example, as shown in FIG. 38, an outer member 330 has disposedtherein one slidably disposed inner tube 336 which has openings 338formed thereon in a constant sequence, and a matching slidably disposedouter tube 332 which has openings 334 formed thereon in a constantsequence of slightly different length or intervals.

In this configuration, as shown in FIG. 39, small linear relationalmovements bring the openings on the outer tube 332 and the inner tube336 into an overlapping configuration.

FIG. 40 illustrates one embodiment of the catheter proximate a treatmentnode, with a limited treatment zone shown around the catheter. Only thedistal end portion of the catheter is shown, labeled generally as 400.The catheter 400 is shown positioned proximate a tissue treatment regionor node 401, marked with an “x” in FIG. 40. The treatment node 401 maybe, for example, the atrioventricular node or any other discrete locusof tissue to be treated and/or mapped.

Catheter 400 includes a catheter body 402, a distal tip 405 and severalECG leads or rings 410, 415, and 420. Each of the ECG rings is staggeredalong the length of the catheter body 402 as shown. The ECG rings may bepart of a bipolar, tripolar, or quadripolar electrocardiographingmapping apparatus. Each of the ECG rings 410, 415, and 420 are made ofan electrically conductive material.

In operation, the catheter is coupled to a source of fluid coolant orcryogen at its proximal end portion (not shown). The coolant is directedto flow in an internal injection lumen or tube (not shown) through tothe distal tip portion 405. Generally, the injection tube includes atleast one orifice or opening though which the coolant exits the tube andflows into a second return lumen (not shown) back to the proximal endportion of the catheter. The orifice included may be a typicalJoule-Thomson gas expansion element, whereupon high pressure coolant ingas phase expands upon exiting the orifice to low pressure, with anattendant drop in temperature. This endothermic process acts to cool theenvironment immediately around the distal tip 405, which itself may bethermally conductive or heat-transmitting, so as to transmit the coolinggenerated by the expansion of gases inside the catheter. The coolingprocess may also be generated by the change in phase of coolant fromliquid to gas, in conjunction with Joule-Thomson expansion. This isgenerally true for coolant that is supplied at mixed gas-liquid phase.

When cooling is thus initiated, the environment around the catheter iscooled to form an iceball, the shape of which is approximately shown bycontour 424 in FIG. 40. This shape is achieved by a conventional coolingcatheter as described above, where only one injection orifice orJoule-Thomson element is employed. However, this shape of coolingcontour is generally not desirable when employing the catheter forcardiac mapping in addition to tissue treatment. For cardiac mapping,the catheter is first used to cool tissue so as to locate a treatmentnode or tissue pathway, as is well-known to those skilled in the art.The treatment node in question is shown in FIG. 40 as point “X”, orlabeled as 401. For a bipolar ECG catheter, node 401 generally lies at alongitudinal point between the first ECG lead, or distal tip 405, andthe second ECG lead, or ring electrode 410. To locate the node 401, thecatheter 400 must be positioned and oriented relative to the node 401 asshown in FIG. 40. If cooling were initiated the catheter 400 wouldproduce a cooling contour or iceball 424 as shown, which would not coverthe treatment node 401. Thus, the catheter would need to be moved andrepositioned to treat or ablate the node 401 after cryomapping such node401.

The present invention is a device, which provides a cryotreatmentcatheter having an extended treatment zone or cooling contour. As usedherein, the term “cryotreatment” shall mean the application of coolingto tissue of varying degrees, from minor temperature changes effectingreversible alterations in cellular structure to cryosurgical ablationand/or removal of tissue. Also as used herein, the term “tissue mapping”or “cryomapping” shall refer to the method, practice, or process ofapplying cooling to tissue and measuring the properties of such tissuein response to said cooling.

Turning now to FIG. 41, the present invention provides the catheter ofFIG. 40, labeled generally as 400, and having, instead of a limitedtreatment zone 424 as shown in FIG. 40, an extended treatment zone 426as shown in FIG. 41. The extended treatment zone is not necessarilylimited to the shape or contour of zone 426, but rather may encompassany contour that is relatively larger than contour 424, extendingsignificantly further away from the distal tip 405, so as to affect notonly the tissue proximate the distal end of the catheter 400, but alsothe tissue along the sides of the catheter body 402.

FIG. 42 illustrates an expanded cross-sectional view of the distal endportion of the catheter 400 of FIG. 41, taken along lines A-A in FIG.41. The distal end portion of the catheter 400 includes, in addition todistal tip 405 and first ECG ring lead 410, a fluid conduit 430 defininga return lumen 432, a first fluid injection port 435, secondary fluidinjection ports 438, a distal end cap 440, one or more electricallyconductive wires or leads 442, a thermally transmissive, electricallyisolating catheter body section 445, a thermally conductive body section450, and one or more seals 452. Furthermore, a longitudinal axis 455 anda transverse axis 460 are shown superimposed on the cross-section toillustrate the spatial orientation of the various elements.

As shown in FIG. 42, catheter 400 includes a fluid injection conduit 430disposed inside of the catheter body 402 to define a fluid return lumen432 therebetween. Coolant is supplied to conduit 430 at its proximal end(not shown) and flows along the right-facing arrows as shown in FIG. 42.The supplied coolant may be any cryogen or cryogenic fluid capable orstable operation at low temperature and high pressure, such nitrousoxide, nitrogen, AZ20, or any suitable refrigerant. The fluid exits theconduit 430 at two or more points, including a first orifice 435 at thedistal end of the conduit 430, and one or more second orifices 438defined by the lateral walls of the conduit 430, at some point lessproximate the distal tip 405 than the first orifice 435. Orifice 435 maybe considered a primary injection port for coolant flowing into thereturn lumen 432, with orifices 438 being the secondary injection ports.However, the relative flow rates of coolant flowing through the orificesmay be of any combination or ratio, depending on the relative size andorientation of the orifices, which may vary considerably. In theembodiment of the present invention shown in FIG. 42, two secondaryorifices 438 are disposed on opposite sides of the lateral wall of theconduit 430, such that only one opening is visible in the illustration.

The secondary orifices 438 are located anywhere along the conduit 430,further away from the distal end 405 along longitudinal axis 455. Theorifices 438 may be staggered along such axis, and may have varyingnormal axes (not shown) that may point in any radial directionperpendicular to the longitudinal axis 455. As used herein, a “normalaxis” shall mean the imaginary straight-line axis in space beingperpendicular to and centered on the plane formed by the orifice,pointing in the direction of fluid flow. For example, the normal axis ofthe first orifice 435 is parallel and coincident with the longitudinalaxis, pointing to the right in FIG. 42.

Further embodiments of the conduit 430 are illustrated in FIGS. 43A and43B, showing two perspective views of the flow conduit of the catheterof FIG. 42. The each of FIGS. 43A and 43B, only the conduit 430 with itsrespective orifices 435 and 438 are shown, including the normal axes foreach orifice, shown as arrows. The rest of the catheter is notillustrated for ease of reference. In FIG. 43A, the secondary orifices438 are staggered along the longitudinal axis 455, having normal axesfacing away from one another. This arrangement leads to a differentshape of a freeze zone or treatment contour around the distal endportion of the catheter. FIG. 43B illustrates yet another arrangement ofprimary orifice 435 with the four secondary orifices. This creates yetanother shape of a freeze zone or treatment contour around the distalend portion of the catheter. The present invention thus encompasses anynumber of arrangements of single or multiple primary and secondaryorifices 435 and 438, so as to create treatment zones of a wide variety,depending on the nature of use intended for the catheter.

Referring back to FIG. 42, as fluid exits the conduit 430, it flowsalong the left-facing arrows of FIG. 42. The return lumen 432 may have apressure that is significantly below the pressure in the flow conduit430. The fluid exiting either or all of the orifices 435 and 438 may betransformed under gas expansion and evaporation to gas phase from liquidphase, thereby altering the gas dynamic and thermodynamic properties ofthe fluid flow. A drop in temperature may create an overall endothermicheat transfer with the environment, thereby cooling any tissuesurrounding the device. To effectively transmit this cooling effect, theouter walls of the catheter 400 must be thermally “transmissive”, orreadily transmit thermal heat flow. Distal end 405 may thus have aconductive end cap 440 made of a thermally conductive material such as ametal. Other suitably strong, resilient yet thermally transmissivematerials may be used.

The gas dynamic expansion and evaporation discussed above is generallycentered about the orifices 435 and 438. That is, mixed phase liquid/gascoolant undergoes the most rapid change in pressure and temperaturedirectly at the locus of the orifices 435 and 438. Since end cap 440primarily surrounds the first orifice 435, the cooling effect providedby such orifice is primarily transmitted through such cap to thesurroundings. The secondary orifices 438 are separated from the primaryorifice 435 along longitudinal axis 455 by a separation length “L” asshown. The portion of the catheter body immediately lateral to orifices438 consists of catheter body section 445. Section 445 forms a portionof the outer wall of catheter 400, and completely surrounds ECG ringelectrode 410. As shown in FIG. 42, ECG ring electrode 410 circumscribesthe outer surface (the surface not in communication with the returnlumen 432) of section 445. An electrical communication wire or lead 442is coupled to the ring electrode.410. Section 445 is made of anelectrically isolating but thermally conductive material like boronnitride, such as is manufactured by Advanced Ceramics Corporation, ofCleveland, Ohio.

Accordingly, ECG ring electrode 410 is completely isolated from the restof the device electrically, thereby being able to function as anindependent terminal for ECG sensing purposes. The wire 442 couples theelectrode 410 to the electrical receiving and monitoring apparatus (notshown). It will be appreciated that the shape and configuration of boththe electrode 410 and catheter body section 445 may vary widely. Theonly requirement is that both elements be separated from the firstorifice 435 by some separation length L along the longitudinal axis.Furthermore, it is advantageous, although not entirely necessary, tohave the electrode 410 disposed at a longitudinal position directly inline with the second orifices 438, such that a transverse axis parallelto the axis 460 running through orifices 438 would also run though thering electrode 410.

Catheter body 402 also includes another section 450 adjacent to section445. Body section 450 is also thermally conductive, but need not beelectrically isolating. Both of sections 445 and 450 serve to transmitthe cooling effect of fluid exiting orifices 438. A sealing element 452may be interposed between section 450 and the rest of catheter body 402.

The net result of the cooling effect of orifice 435 and orifices 438 isto create an elongate contour 426 whereby tissue proximate the catheteris treated. This extended treatment zone covers a tissue node 401 asshown. Node 410 is longitudinally positioned at some point alongseparation length L, having transverse axis 460 running therethough.Separation length L may range anywhere from 1 mm to 50 mm. As shown inFIG. 42, this positional relationship may vary. Yet, the object of theinvention to provide an extended treatment or freeze zone around thedistal tip of catheter 400 is accomplished regardless of the particularposition of treatment node 401, the example used in the drawing figuresbeing merely one of a number of applications for which the presentinvention may be used.

FIG. 44 illustrates a cross-sectional view of yet another embodiment ofthe catheter discussed in FIGS. 41 and 42, and labeled generally as 500.Catheter 500 has a distal end portion, which includes athermally-transmissive end cap 505 at its tip. The catheter 500 furtherincludes a first ECG ring electrode 507 disposed between two sections ofthe catheter shaft 508. The catheter 500 also includes a centralinjection tube 510 having injection orifices 511 and 512. The tube 510is circumscribed by the shaft 508 to define an expansion chamber 514proximate the end cap 505 and first orifice 511, and a fluid returnlumen further proximate the second orifice 512.

Cryogen is injected through the tube 510 to flow out into the expansionchamber 514 and return lumen 515, which both serve as spaces wherein thefluid is expanded and evaporated to cool the structures surrounding it.A source of vacuum may be coupled to the proximal end portion (notshown) of the catheter 500 to provide a negative pressure gradient asthe expanded cryogen flows away from the tip. The flow into the returnlumen 515 is shown by arrows designated as F_(in), and represents theflow rate of cryogen into the control volume CV as shown. The flow outof the control volume CV is shown by the arrows designated as F_(out),and represents the mass or volumetric flow rate of cryogen exiting thecontrol volume CV. The control volume CV effectively covers the entiredistal end portion of the catheter 500, and incorporates the locus ofsources of cooling or endothermic heat flow with respect to theenvironment, schematically represented by the arrow Q as shown.

Varying the flow rates Fin and Fout may effect the cooling. Thus, theflow may not always be steady state, where F_(in)=F_(out). For example,in one application of the invention the flow rates may be equal, whereF_(in)=F_(out) and the fluid entering the expansion chamber 514 andreturn lumen 515 may be just equal to the amount of fluid exiting thedistal end portion or control volume CV. This would be the case ofsteady state flow. In another application, the initial incoming flowF_(in) would be much greater than Fout (F_(in)>>F_(out)), resulting inan unsteady flooding of the tip region, and creating a different coolingprofile. The varying flow rates would in turn affect the time andamplitude response characteristics of heat flow Q, depending on thedesired cooling profile.

Furthermore, catheter 500 includes an electrically isolating, yetthermally conductive, buffer element 525 at the distal end of thecatheter shaft 508. The end cap 505 is attached not to the shaft 508 butto such element 525, thereby isolating the end cap 505 from the rest ofthe catheter 500. This reduces electrical or signal noise duringoperation of the catheter 500 as described above, such as forcryomapping.

A variety of modifications and variations of the present invention arepossible in light of the above teachings. Specifically, although manyembodiments are illustrated being slender and flexible, otherembodiments may be thick and rigid, and introduced into the bodydirectly through incisions or through structures such as trocars. Usingnanotechnology and miniaturized valving may also control the opening andclosing of the catheter openings. Furthermore, although some of theillustrated devices are particularly well suited for cardiac procedures,the same embodiments and others are equally suited to other organsand/or any body portion that would benefit from the application ofthermal energy. For example, the illustrated devices may be used fortreating arteries for restenosis or portions of the GI tract to stopbleeding or portions of the GU tract to treat spasm, inflammation,obstruction or malignancy. Thus, the devices as shown are not to belimited to catheters but should be viewed more broadly as cryogenicstructures or portions thereof. It is therefore understood that, withinthe scope of the appended claims, the present invention may be practicedotherwise than as specifically described hereinabove. All referencescited herein are expressly incorporated by reference in their entirety.

It will be appreciated by persons skilled in the art that the presentinvention is not limited to what has been particularly shown anddescribed herein above. In addition, unless mention was made above tothe contrary, it should be noted that all of the accompanying drawingsare not to scale. A variety of modifications and variations are possiblein light of the above teachings without departing from the scope andspirit of the invention, which is limited only by the following claims.

1. A tissue mapping and cryotreatment catheter, comprising: an elongatecatheter body having a distal tip, a fluid injection conduit disposedinside the catheter body and defining a return lumen therein, the fluidinjection conduit having a distal end portion, the distal end portiondefining two or more injection orifices including a first orifice and asecond orifice, the first orifice being proximate the distal tip, thesecond orifice being longitudinally offset along the fluid injectionconduit to be less proximate the distal tip than the first orifice; andat least one electrode disposed on the catheter body proximate thedistal tip, the at least one electrode being longitudinally offset fromthe distal tip to be proximate the second orifice.
 2. The catheter ofclaim 1, wherein the distal tip is a first electrocardiogram lead andthe at least one electrode is a second electrocardiogram lead.
 3. Thecatheter of claim 1, further comprising: a thermally transmissive andelectrically insulating first body section disposed on the catheter bodyand longitudinally offset along the catheter body from the distal tip,the first body section surrounding the at least one electrode such thatthe distal tip is electrically isolated from the at least one electrode.4. The catheter of claim 3, wherein the first body section includes anouter surface and the at least one electrode is a circumferential ringdisposed about the outer surface of the first body section of thecatheter body.
 5. The catheter of claim 3, further comprising: athermally conductive second body section disposed on the catheter bodyadjacent the first body section and longitudinally offset along thecatheter body from the distal tip to be less proximate the distal tipthan the first body section.
 6. A tissue treatment catheter, comprising:an elongate catheter body having a thermally conductive distal tip anddefining a return lumen therein along a longitudinal axis, a coolantinjection tube disposed in the return lumen substantially parallel tothe longitudinal axis, and having a proximal end portion in fluidcommunication with a supply of cryogen and a distal end portionproximate the distal tip, the distal end portion defining two or moreinjection orifices disposed longitudinally along the distal end portion,wherein the distal end portion of the coolant injection tube definesfirst, second and third orifices having first, second, and third normalaxes, respectively, the first normal axis being substantially parallelto the longitudinal axis, and the second and third normal axes beingsubstantially perpendicular to the longitudinal axis, and a thermallyconductive section disposed on the catheter body proximate the distaltip.
 7. The catheter of claim 6, wherein second and third normal axesare coincident lines in opposite direction to one another.
 8. Thecatheter of claim 6, wherein the distal end portion of the coolantinjection tube defines a separation length along the longitudinal axisbetween the first orifice and the second orifice, the separation lengthbeing in a range between 1 mm and 50 mm.
 9. The catheter of claim 6,further comprising: at least one electrode disposed on the catheter bodyproximate the distal tip, the at least one electrode beinglongitudinally offset from the distal tip by the separation length. 10.The catheter of claim 9, wherein the distal tip is a firstelectrocardiogram lead and the at least one electrode is a secondelectrocardiogram lead.
 11. The catheter of claim 9, wherein thethermally conductive section includes an outer surface and the at leastone electrode is a circumferential ring disposed about the outer surfaceof the thermally conductive section of the catheter body.
 12. Thecatheter of claim 11, wherein the thermally conductive section iselectrically insulating.
 13. The catheter of claim 9, furthercomprising: an electrically conductive wire coupled to the at least oneelectrode.
 14. A method of treating tissue using a catheter havingdistal and proximal end portions, comprising: inserting the distal endportion of a catheter into a body lumen proximate a target region oftissue, the distal end portion including a thermally conductive capfixed to a catheter body, and a fluid injection conduit disposed insidethe catheter body and defining a return lumen therein, the fluidinjection conduit further defining two or more injection orificeslongitudinally separated along the fluid injection conduit, wherein thecatheter body includes at least one electrode disposed on the catheterbody proximate the thermally conductive cap, the at least one electrodebeing longitudinally offset from the distal end to be proximate thesecond orifice; supplying a flow of fluid cryogen to the proximal endportion of the catheter, the fluid injection conduit being in fluidcommunication with the flow of fluid cryogen; injecting the flow offluid cryogen through the two or more injection orifices; and expandingthe flow of fluid cryogen in the return lumen to cool the target tissueregion.
 15. The method of claim 14, further comprising: mapping a tissuenode in the target region of tissue with the thermally conductive capand the at least one electrode.
 16. The method of claim 15, furthercomprising: cooling the tissue node in the tissue target region aftermapping the tissue node, without moving the distal end portion of thecatheter.
 17. A method of treating tissue using a catheter having distaland proximal end portions, comprising: inserting the distal end portionof a catheter into a body lumen proximate a target region of tissue, thedistal end portion including a thermally conductive cap fixed to acatheter body, and a fluid injection conduit disposed inside thecatheter body and defining a return lumen therein, the fluid injectionconduit further defining two or more injection orifices longitudinallyseparated along the fluid injection conduit; supplying a flow of fluidcryogen to the proximal end portion of the catheter, the fluid injectionconduit being in fluid communication with the flow of fluid cryogen;injecting the flow of fluid cryogen through the two or more injectionorifices; expanding the flow of fluid cryogen in the return lumen tocool the target tissue region; and directing the flow of fluid cryogenfrom the return lumen away from the distal end portion of the catheterat a first flow rate, wherein the injecting of the flow of fluid cryogenthrough the two or more injection orifices is at a second flow rate;wherein the first flow rate is less than the second flow rate.
 18. Acryogenic catheter comprising: an elongated thermally-transmissiveregion defining a substantially longitudinal axis therethrough, whereinthe elongated thermally-transmissive region includes a plurality ofthermally-transmissive segments in spaced apart relation; and acryogenic dispensing lumen substantially traversing the elongatedthermally-transmissive region, including at least one fluid outletdirecting a portion of the cryogenic fluid radially towards theelongated thermally-transmissive region.
 19. The cryogenic catheteraccording to claim 18, further including a plurality of fluid outletsarranged in special relation with the plurality ofthermally-transmissive segments.
 20. A cryogenic catheter comprising: anelongated thermally-transmissive region defining a substantiallylongitudinal axis therethrough; a cryogenic dispensing lumensubstantially traversing the elongated thermally-transmissive region,including at least one fluid outlet directing a portion of the cryogenicfluid radially towards the elongated thermally-transmissive region; andan electrode ring circumferentially disposed around the distal end ofthe elongated thermally-transmissive region.